bplib: Python library for bilinear pairings

The bplib is a library implementing support for computations on groups supporting bilinear pairings, as used in modern cryptography. It is based on the OpenPairing library by Diego Aranha (https://github.com/dfaranha/OpenPairing), which is itself based on, and compatible with, OpenSSL math functions (bn and ec). The bplib is compatible with petlib types including petlib.bn and the group G1 is a petlib.ec EC group. Along with petlib, they provide easy to use support for maths and ciphers used in modern Privacy Enhancing Technologies.